This application claims the priority of Korean Patent Application No. 2001-63209, filed Oct. 13, 2002 in the Korean Intellectual Property Office, which is incorporated herein in its entirety by reference.
Field of the Invention
The present invention relates to a database management system (DBMS), and more particularly, to a method for deleting instances of classes that have a vertical relationship (inheritance relationship) or a horizontal relationship (1:1, 1:N, or M:N relationship) that are stored as object identifier (OID) sets in a main-memory resident object-relational database management system (ORDBMS).
Description of the Related Art
A database management system (DBMS) is a system software that is capable of maintaining the consistency of large amounts of information and searching data effectively. With the exponential growth of Internet traffic, information service provider have faced finding solutions for the very-high-speed information services on the Internet. There has been also a growing need for the processing of various types of information and quick access to desired data using the Internet. This growing need requires changes in the structure and paradigm of the conventional DBMS which is a foundation of an information system. One of the changes is the rise in the prevalence of a main-memory resident DBMS in which hole database resides in a main memory device. Main memory-resident database management solutions have gained widespread acceptance in the marketplace after years of research and development in both academic and commercial settings. These technologies offer dramatic performance boosts over disk-based RDBMS systems, even when those systems are running with all of their data buffered in main memory.
The main-memory resident DBMS can be also used as a front-end of conventional disk-based DBMSs to increase the performance of a system. At present, the main-memory resident DBMS is widely used as a front-end DBMS of a disk-based DBMS or a built-in DBMS around the world.
A main-memory resident object-relational (OR) DBMS having the characteristics of the existing main-memory resident DBMS and being capable of processing data at a high speed has recently been developed. The ORDBMS can flexibly process data through object-oriented queries.
Also each object includes an object identifiers (OIDs) and, thus, can represent horizontal and vertical relationships between classes of an object-relational database. The ORDBMS supports relationships of 1:1, 1:N, or M:N types between classes to model the horizontal relationship between classes. When expressing the relationship between classes, an OID acts as a pointer to a related object, thereby increasing an efficiency ratio of query processing. That is, when there is a request for two or more classes to be joined, the use of OIDs makes it possible to obtain a desired result by directly joining the classes without a burden of an additional memory and cost for join operation.
As previously mentioned, the main-memory resident ORDBMS stores the vertical and horizontal relationships among classes as OID sets. For this reason, if OID pointers related to a class instance are not correctly and completely deleted when deleting the class instances, OID pointers indicating the deleted class instance remain in a certain class, and it becomes a dangling pointer. This would deteriorate the consistency within database. Accordingly, it is required to completely delete class instances and their OID pointers to another classes.